1. Field of the Invention
The present invention relates to a transmitter device, a transmitting method, a receiver device, a receiving method, a communication system, and a program storage medium, and, more particularly, a transmitter device, a transmitting method, a receiver device, a receiving method, a communication system, and a program storage medium, for preventing unauthorized copying of content data and for limiting the number of uses of the content data.
2. Description of the Related Art
Providers, who provide content data such as images and sound, or computer programs to a user, typically encrypt the content data before supplying them to the user in order to prevent unlimited copying of the content data.
In this environment, only an authorized user who owns a predetermined encryption/decryption key can use the content data.
To further strongly prevent unauthorized use of the content data, some devices use a technique which allows a unit for reproducing content data and a unit for driving a recording medium storing the content data to mutually or cross authenticate each other.
To limit the number uses of the content data, a provider stores, in a recording medium, data to be used for management of the number of uses of the content data, together with the content data, and provides these data to a user. When the device for driving the recording medium reads the content data stored in the recording medium, the device determines, based on the data for the management of the number of uses of the content data, whether the number of reads of the content data exceeds a predetermined number. When the number of reads of the content data exceeds the predetermined number, the provider inhibits the use of the content data.
The data managing the number of uses is stored in a recording medium together with the content data. If the data managing the number of the uses is transferred back to the original recording medium after the use of the content data, the user uses the content data unlimited number of times.
When the content data is moved to a second recording medium, the data managing the number of the uses may be moved to a third recording medium together with the content data. After the content data is moved to the second recording medium, the data managing the number of the uses may be moved back to the original recording medium from the third recording medium along with the content data. In this way, a user may copy the content data unlimited number of times.
In the movement process of the content data to another recording medium, the copying of the content data is repeatedly performed unlimited number of times by impeding the deletion of the content data or the data managing the number of the uses. The user can freely use the content data in a limitless fashion.